Impeller and motor assembly

ABSTRACT

A breathing assistance apparatus has a pressurised gases source featuring a lightweight impeller with a plastic shaft. The impeller is shroudless. The plastic shaft is supported within the stator by a bearing structure. A resilient motor mount couples the stator and the housing and provide compliance and/or damping for the motor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a gases supply and gases humidificationapparatus, particularly but not solely for providing respiratoryassistance to patients or users who require a supply of gas for thetreatment of diseases such as Obstructive Sleep Apnea (OSA), snoring, orChronic Obstructive Pulmonary Disease (COPD) and the like. Inparticular, this invention relates to a compressor or blower for use ina gases supply apparatus which in use is integral with the gases supplyapparatus.

2. Description of the Related Art

Devices or systems for providing a humidified gases flow to a patientfor therapeutic purposes are well known in the art. Systems forproviding therapy of this type, for example CPAP therapy, have astructure where gases at the required pressure are delivered from ablower (also known as a compressor, an assisted breathing unit, a fanunit, a flow generator or a pressure generator) to a humidifier chamberdownstream from the blower. As the gases are passed through the heated,humidified air in the humidifier chamber, they become saturated withwater vapour. The gases are then delivered to a user or patientdownstream from the humidifier, via a gases conduit.

Humidified gases can be delivered to a user from a modular system thathas been assembled from separate units (that is, a system where thehumidifier chamber/heater and the breathing unit/blower are separateitems) connected in series via conduits. A schematic view of a user 1receiving air from a modular assisted breathing unit and humidifiersystem (together or separately a “breathing assistance apparatus”) isshown in FIG. 1. Pressurised air is provided from an assisted breathingunit or blower 2 a via a connector conduit 10 to a humidifier chamber 4a. Humidified, heated and pressurised gases exit the humidifier chamber4 a via a user conduit 3, and are provided to the patient or user 1 viaa user interface 5.

It is becoming more common for integrated blower/humidifier systems tobe used. A typical integrated system (“breathing assistance apparatus”)consists of a main blower or assisted breathing unit which provides apressurised gases flow, and a humidifier unit that mates with or isotherwise rigidly connected to the blower unit. This mating occurs forexample by a slide-on or push connection, so that the humidifier is heldfirmly in place on the main blower unit. A schematic view of the user 1receiving air from an integrated blower/humidifier unit 6 is shown inFIG. 2. The system operates in the same manner as the modular systemshown in FIG. 1, except that humidifier chamber 4 b has been integratedwith the blower unit to form the integrated unit 6.

The user interface 5 shown in FIGS. 1 and 2 is a nasal mask, coveringthe nose of the user 1. However, it should be noted that in systems ofthese types, a mask that covers the mouth and nose, a full face mask, anasal cannula, or any other suitable user interface could be substitutedfor the nasal mask shown. A mouth-only interface or oral mask could alsobe used. Also, the patient or user end of the conduit can be connectedto a tracheostomy fitting, or an endotracheal intubation.

U.S. Pat. No. 7,111,624 includes a detailed description of an integratedsystem. A ‘slide-on’ water chamber is connected to a blower unit in use.A variation of this design is a slide-on or clip-on design where thechamber is enclosed inside a portion of the integrated unit in use. Anexample of this type of design is shown in WO 2004/112873, whichdescribes a blower, or flow generator 50, and an associated humidifier150.

For these systems, the most common mode of operation is as follows: airis drawn by the blower through an inlet into the casing which surroundsand encloses at least the blower portion of the system. The blower(controlled by a microcontroller, microprocessor or similar) pressurisesthe air stream from the flow generator outlet and passes this into thehumidifier chamber. The air stream is heated and humidified in thehumidifier chamber, and exits the humidifier chamber via an outlet. Aflexible hose or conduit is connected either directly or indirectly tothe humidifier outlet, and the heated, humidified gases are passed to auser via the conduit. This is shown schematically in FIG. 2.

Impeller type fans or blowers are most commonly used in breathingsystems of this type. An impeller blade unit is contained within animpeller housing. The impeller blade unit is connected to a drive ofsome form by a central spindle. A typical impeller housing is shown inFIGS. 3 and 4. A typical rotating impeller unit 54, having a pluralityof blades 151 and a shroud 152, which in use is located inside thehousing is shown in FIGS. 5 and 6. Air is drawn into the centre of theimpeller unit through an aperture, and is then forced outwards from thecentre of the housing towards an exit passage (usually located to oneside of the housing) by the blades of the rotating impeller unit.

Generally, domestic users receive treatment for sleep apnea or similar.It is most common for a nasal mask, or a mask that covers both the mouthand nose, to be used. If a nasal mask is used, it is common to strap ortape the mouth closed, so that the use of the system is effective (mouthleak and the associated pressure drop are substantially reduced oreliminated). For the range of flows dictated by the user's breathing,the CPAP device pressure generator provides a flow of gases at asubstantially constant pressure. The pressure can usually be adjustedbefore use, or during use, either by a user, or a medical professionalwho sets up the system. Systems that provide variable pressure duringuse are also known—for example BiPAP machines that provide two levels ofpressure: One for inhalation (IPAP) and a lower pressure during theexhalation phase (EPAP). Variable pressure or constant pressure systemsare all “breathing assistance apparatus”

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved impelleror blower/compressor for use with a breathing assistance apparatus or animproved breathing assistance apparatus.

In one aspect the present invention may be said to consist in abreathing assistance apparatus comprising: a pressurised gases sourcecomprising: a gases inlet, a gases outlet adapted to emit pressurisedgases to an outlet of the breathing assistance apparatus, and alightweight impeller on a rotatable plastic shaft.

Preferably the lightweight impeller is shroudless or otherwise hasreduced material.

Preferably the breathing assistance apparatus further comprises a motorwith a stator, wherein the rotatable plastic shaft is located within thestator, and the motor further comprises at least one bearing structureto support the rotatable plastic shaft within the stator, the bearingstructure having one or more bearing mounts.

Preferably the bearing mounts provide compliant support to the rotatableshaft.

Preferably the motor further comprises a rotor within the stator, theplastic shaft being formed and coupled to the rotor by injectionmoulding.

In another aspect the present invention may be said to consist in Abreathing assistance apparatus comprising: a motor comprising arotatable plastic shaft located within a stator, a bearing structure tosupport the rotatable shaft in the stator, the bearing structure havingone or more bearing mounts.

Preferably the bearing mounts provide compliant support to the rotatableshaft.

Preferably the motor further comprises a rotor within the stator, theplastic shaft being formed and coupled to the rotor by injectionmoulding.

In another aspect the present invention may be said to consist in abreathing assistance apparatus comprising: a pressurised gases sourcecomprising: a housing, a gases inlet, a gases outlet adapted to emitpressurised gases to an outlet of the breathing assistance apparatus, amotor with a rotatable plastic shaft and at least one bearing structureto support the rotatable shaft within a stator, the bearing structurehaving one or more flexible and/or resilient bearing mounts to providecompliance and/or preload and/or damping for the rotatable shaft, alightweight impeller coupled to the rotatable plastic shaft, a flexibleand/or resilient motor mount that couples the stator and the housing toprovide compliance and/or damping for the motor, a partition to definefirst and second interior regions within the housing, wherein the firstand second regions are fluidly connected by a crescent shaped openingformed in or by the partition.

Preferably the lightweight impeller is shroudless or otherwise hasreduced material.

Preferably the motor further comprises a rotor within the stator, theplastic shaft being formed and coupled to the rotor by injectionmoulding.

In another aspect the present invention may be said to consist in amethod of manufacturing a shaft and rotor assembly for a motorcomprising: inserting a rotor with a central opening into a first mouldpart, supporting a shaft extended through the central opening, couplinga second mould part to the first mould part to create a mould cavityaround the central opening, injection moulding a plastic insert betweenthe plastic shaft and the central opening to couple the plastic shaft tothe rotor.

In another aspect the present invention may be said to consist in amethod of manufacturing a shaft and rotor assembly for a motorcomprising: inserting a rotor with a central opening into a first mouldpart, coupling a second mould part to the first mould part to create amould cavity around the central opening, injection moulding a plasticshaft that extends through and couples to the central opening of therotor.

Preferably the motor comprises a plastic rotatable shaft extendingthrough an opening in a magnet rotor and being coupled thereto.

Also described is a breathing assistance apparatus comprising: apressurised gases source comprising: a gases inlet, a gases outletadapted to emit pressurised gases to an outlet of the breathingassistance apparatus, and a lightweight impeller.

Preferably lightweight impeller is shroudless or otherwise has reducedmaterial.

Preferably lightweight impeller is formed in one piece.

Preferably the lightweight impeller has a radius of between 15 and 60mm.

Preferably the lightweight impeller has a mass of less than 2 grams andpreferably between 0.8 and 1.8 grams.

Preferably the lightweight impeller has a pressure to inertia to radiusratio greater than 50:1 Pa per gram*mm, and preferably greater than 80:1Pa per gram*mm.

Preferably the lightweight impeller has a moment of inertia to radiusratio less than 15 g*mm and preferably within the range of 8 to 12 g*mm.

Preferably the lightweight impeller has a blade sweep volume to a bladevolume ratio of 16:1 or greater.

Preferably the impeller is a centrifugal impeller rotatable about acentral axis.

Preferably the breathing assistance apparatus comprises a motor fordriving the impeller wherein the motor is operated using field orientedcontrol.

Preferably the gases source further comprises a housing having upper andlower internal surfaces that enclose the impeller, and wherein theimpeller has a plurality of blades that are substantially open to theupper and lower internal surfaces of the housing by virtue of beingshroudless.

Preferably the housing forms part of or is integrated with the breathingassistance apparatus.

Preferably the gases source further comprises a partition to definefirst and second interior regions within the housing, wherein the firstand second regions are fluidly connected by an opening formed in or bythe partition.

Preferably the opening formed in or by the partition is at leastpartially circumferential.

Preferably opening formed in or by the partition is crescent shaped.

Preferably the first region is defined by the housing and the partitionand comprises the gases inlet.

Preferably the second region is defined by the housing and the partitionand comprises the gases outlet.

Preferably the impeller has an axis of rotation, the partition extendingradially from the axis of rotation.

Preferably the housing further comprises a volute in the second region.

Preferably the opening is proximate the periphery of the volute.

Preferably the impeller is located within the first region.

Preferably a distal end of the impeller blades curve in the direction ofblade rotation.

Preferably the breathing assistance apparatus further comprises a motor,the motor comprising: a rotatable shaft located within a stator, and atleast one bearing structure to support the rotatable shaft within thestator, the bearing structure having one or more bearing mounts.

Preferably the bearing mount provides compliant support to the rotatableshaft.

Preferably an outer portion of the one or more bearing mounts engagesthe stator and/or a stator frame and/or other structure.

Preferably an outer portion of the one or more bearing mounts engagesthe stator and/or frame of the stator.

Preferably the stator comprises a stator frame, an inner surface of thestator frame engages with the bearing structure.

Preferably the bearing structure further comprises one or more bearingssupported by the bearing mounts about the axis of the rotatable shaft.

Preferably the pressurised gases source has a housing and the breathingapparatus further comprises a motor mount that couples the stator andthe housing to provide compliant support to the motor.

Preferably the bearing mount and/or motor mount are flexible and/orresilient.

Preferably the volute has a tongue at least partially defining atransition between the volute and the gases outlet, the tongue locatedin the second interior region.

Preferably the bearing mounts have a curved annular body and whenengaged with the stator and/or stator frame and/or other structure theannular body is coerced into an engaged configuration that providespreload to the one or more bearings.

Preferably the bearing mount is made from a material that providesresilience and/or flexibility to provide preload when in the engagedconfiguration.

Preferably the bearing mounts are made from a material that providesdamping.

Preferably the motor is operated using field oriented control.

Also described is a breath assistance apparatus comprising: a motorcomprising a rotatable shaft located within a stator, a bearingstructure to support the rotatable shaft in the stator, the bearingstructure having one or more bearing mounts.

Preferably the bearing mounts provide compliant support to the rotatableshaft.

Preferably an outer portion of the one or more bearing mounts engagesthe stator and/or a stator frame and/or other structure.

Preferably the stator comprises a stator frame, an inner surface of thestator frame engaging with the bearing structure.

Preferably the bearing structure further comprises one or more bearingssupported by the bearing mounts about the axis of the rotatable shaft.

Preferably the bearing mount is flexible and/or resilient.

Preferably the bearing mounts have a curved annular body and whenengaged with the stator and/or stator frame and/or other structure theannular body is coerced into an engaged configuration that providespreload to the one or more bearings.

Preferably the bearing mount is made from a material that providesresilience and/or flexibility to provide preload when in the engagedconfiguration.

Preferably the bearing mounts are made from a material that providesdamping.

Also described is a pressurised gases source comprising: a centrifugalimpeller driven by a motor within a housing, the housing having a gasesinlet, a gases outlet and a partition to define first and secondinterior regions wherein the first and second regions are fluidlyconnected by an opening in the partition.

Preferably the first region is defined by the housing and the partitionand comprises the gases inlet.

Preferably the second region is defined by the housing and the partitionand comprises the gases outlet.

A pressurised gases source according to any of the above used in abreathing assistance apparatus according to any of the above.

Also described is a breathing assistance apparatus comprising: apressurised gases source comprising: a housing a gases inlet,

a gases outlet adapted to emit pressurised gases to an outlet of thebreathing assistance apparatus, a motor with a rotatable shaft and atleast one bearing structure to support the rotatable shaft within astator, the bearing structure having one or more flexible and/orresilient bearing mounts to provide compliance and/or preload and/ordamping for the rotatable shaft, a lightweight impeller coupled to therotatable shaft, a flexible and/or resilient motor mount that couplesthe stator and the housing to provide compliance and/or damping for themotor a partition to define first and second interior regions within thehousing, wherein the first and second regions are fluidly connected by acrescent shaped opening formed in or by the partition.

Preferably the lightweight impeller is shroudless or otherwise hasreduced material.

Preferably the lightweight impeller is formed in one piece.

Preferably the lightweight impeller has a radius of between 15 and 60mm.

Preferably the lightweight impeller has a mass of less than 2 grams andpreferably between 0.8 and 1.8 grams.

Preferably the lightweight impeller has a pressure to inertia to radiusratio greater than 50:1 Pa per gram*mm, and preferably greater than 80:1Pa per gram*mm.

Preferably the lightweight impeller has a moment of inertia to radiusratio less than 15 g*mm and preferably within the range of 8 to 12 g*mm.

Preferably the lightweight impeller has a blade sweep volume to a bladevolume ratio of 16:1 or greater.

Also described is a pressurised gases source comprising: a gases inlet,a gases outlet, a motor with a shaft, and a lightweight impellerconnected to the motor and rotatable to draw gases from the inlet andemit gases through the outlet, wherein the impeller is shroudless orotherwise has reduced material.

Preferably the impeller is a centrifugal impeller rotatable about acentral axis.

Preferably the gases source further comprises a housing having upper andlower internal surfaces that enclose the impeller, and wherein theimpeller has a plurality of blades that are substantially open to theupper and lower internal surfaces of the housing by virtue of beingshroudless.

Preferably the housing forms part of or is integrated with a CPAPmachine.

Preferably the gases source further comprises a partition to definefirst and second interior regions within the housing, wherein the firstand second regions are fluidly connected by an opening formed in or bythe partition.

Preferably the opening formed in or by the partition is at leastpartially circumferential.

Preferably the first interior region is defined by the housing and thepartition and comprises the gases inlet.

Preferably the second interior region is defined by the housing and thepartition and comprises the gases outlet.

Preferably the impeller has an axis of rotation, the partition extendingradially from the axis of rotation.

Preferably the housing further comprises a volute in the second region.

Preferably the opening is proximate the periphery of the volute.

Preferably the impeller is located within the first region.

Preferably a distal end of the impeller blades curve in the direction ofblade rotation.

Preferably the further comprising a motor, the motor comprising: arotatable shaft located within a stator, and at least one bearingstructure to support the rotatable shaft, the bearing structure havingone or more bearing mounts engaged and axially aligned with the statorto provide compliant support to the rotatable shaft.

Preferably an outer portion of the one or more bearing mounts engagesthe stator.

Preferably the stator comprises a stator frame, an inner surface of thestator frame engaging with the bearing structure.

Preferably the bearing structure further comprises one or more bearingssupported by the bearing mounts about the axis of the rotatable shaft.

Preferably the pressurised gases source further comprises a motor mountthat couples the stator frame and the housing to provide compliantsupport to the motor.

Preferably the bearing mount is flexible and/or resilient.

Preferably the volute has a tongue at least partially defining atransition between the volute and the gases outlet, the tongue locatedin the second interior region.

Preferably the motor is vector controlled.

In this specification where reference has been made to patentspecifications, other external documents, or other sources ofinformation, this is generally for the purpose of providing a contextfor discussing the features of the invention. Unless specifically statedotherwise, reference to such external documents is not to be construedas an admission that such documents, or such sources of information, inany jurisdiction, are prior art, or form part of the common generalknowledge in the art

The term “comprising” as used in this specification means “consisting atleast in part of”. When interpreting each statement in thisspecification that includes the term “comprising”, features other thanthat or those prefaced by the term may also be present. Related termssuch as “comprise” and “comprises” are to be interpreted in the samemanner.

It is intended that reference to a range of numbers disclosed herein(for example, 1 to 10) also incorporates reference to all rationalnumbers within that range (for example, 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5,7, 8, 9 and 10) and also any range of rational numbers within that range(for example, 2 to 8, 1.5 to 5.5 and 3.1 to 4.7).

To those skilled in the art to which the invention relates, many changesin construction and widely differing embodiments and applications of theinvention will suggest themselves without departing from the scope ofthe invention as defined in the appended claims. The disclosures and thedescriptions herein are purely illustrative and are not intended to bein any sense limiting. Where specific integers are mentioned hereinwhich have known equivalents in the art to which this invention relates,such known equivalents are deemed to be incorporated herein as ifindividually set forth. The invention consists in the foregoing and alsoenvisages constructions of which the following gives examples only.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred form of the present invention will now be described withreference to the accompanying drawings.

FIG. 1 shows a schematic view of a modular assisted breathing unit andhumidifier system.

FIG. 2 shows a schematic view of a modular assisted breathing unit andhumidifier system.

FIG. 3 shows a plan view of an example of a blower unit.

FIG. 4 shows a side view of the blower unit of FIG. 3.

FIG. 5 shows a profile view of an impeller.

FIG. 6 shows another profile view of an impeller.

FIG. 7 shows a profiled view of a gases supply unit.

FIG. 8 shows an exploded view of the gases supply unit of FIG. 7.

FIG. 9 shows an internal view of a gases supply unit (viewed fromunderneath).

FIG. 10 shows a profiled view of the gases supply unit of FIG. 9.

FIG. 11 shows a plan view of the top side of a blower unit of oneembodiment.

FIG. 12 shows a plan view of the bottom side of the blower unit of FIG.11.

FIG. 13 shows a profile view of the bottom side of the blower unit ofFIG. 12

FIG. 14A shows a plan view of the impeller with no shroud according toone embodiment.

FIG. 15A shows a profile view of the impeller of FIG. 14 a with noshroud.

FIG. 14B shows a plan view of the impeller with reduced shroud materialaccording to one embodiment.

FIG. 15B shows a profile view of the impeller of FIG. 14 b with reducedshroud material.

FIG. 14C shows a plan view of the impeller with a web structure.

FIG. 15C shows a profile view of the impeller of FIG. 14 c with a webstructure.

FIG. 16 shows an exploded view of the preferred housings and impeller ofone embodiment.

FIG. 17 shows a plan view of the lower housing, partition and impellerof one embodiment.

FIG. 18 shows a profile view of the components of FIG. 17.

FIG. 19 shows a cross sectional view of the motor and impeller of oneembodiment.

FIG. 20 shows a motor mounting structure one embodiment.

FIG. 21 shows the motor mounting structure with a motor and impeller ofone embodiment.

FIG. 22A is a graph of average sound pressure levels of an earlierblower unit.

FIG. 22B is a graph of average sound pressure levels of the blower unitof the present invention.

FIG. 23 shows the motor mounting structure with a motor and impeller ofa second embodiment.

FIG. 24 shows a stator lamination of the second embodiment.

FIG. 25 shows a pole face of the second embodiment.

FIG. 26 shows a bearing mount of the second embodiment.

FIG. 27 shows a cross sectional view of the motor and impeller of thesecond embodiment.

FIG. 28 shows a motor mounting structure of the second embodiment.

FIG. 29A is a pressure response graph of an earlier blower unit.

FIG. 29B is a pressure response graph of the blower unit of the presentinvention.

FIGS. 30A, 30B show a metal shaft and magnet rotor assembly forming partof a motor.

FIG. 31 shows the metal shaft of the assembly in FIGS. 30A, 30B.

FIG. 32 shows a plastic shaft and magnet rotor assembly forming part ofanother embodiment of the motor.

FIGS. 33A and 33B show an injection moulding tool for manufacturing theplastic shaft and rotor assembly of FIG. 32.

FIG. 34 shows a flow diagram of an injection moulding process for themetal shaft/insert rotor assembly.

FIG. 35 shows a flow diagram of an injection moulding process for theplastic shaft rotor assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will be described with reference to a breathingassistance apparatus/system where the humidifier chamber is integratedwith the gases supply unit (also referred to as a respirator unit orblower unit). However, it should be noted that the system is equallyapplicable to a modular system.

The present invention relates to a lightweight/low inertia impeller. Thelightweight nature of the impeller provides low inertia.

An example of an integrated gases supply unit 7 with which embodies thepresent invention is shown in FIG. 7—this is one example and should notbe limiting. The integrated unit 7 comprises two main parts: a gasessupply unit or blower unit 8 and a humidifier unit 9. Humidificationunit 9 is partially enclosed within the external shell 80 of the blowerunit 8 in use, except for the top of the humidification unit 9. It alsocomprises an internal controller 14 such as a microcontroller,microprocessor or similar for controlling the blower unit and otheroperations, such as that shown schematically in dotted lines. It is notnecessary to describe the structure and operation of the humidificationunit 9 in detail in order to fully describe the present invention.

The body of the gases supply unit 8 has the form of a generallyrectangular block with substantially vertical side and rear walls, and afront face that is angled slightly rearwards (all the walls can beangled inwards slightly if required). In the preferred embodiment, thewalls, base and top surface are all manufactured and connected as far aspossible to minimise the occurrence of seams, and any necessary seamsare sealed. As shown in FIG. 7, the gases supply unit 8 includes acontrol knob 11, located on the lower section of the front face of thegases supply unit 8, with a control display 12 located directly abovethe knob 11. A patient outlet 30 is shown passing out of the rear wallof the gases supply unit 8. In the preferred embodiment, the free end ofthe outlet 30 faces upwards for ease of connection. The patient outlet30 is adapted to allow both pneumatic and electrical connection to oneend of a conduit—e.g. conduit 3—running between the integrated unit 7and a patient interface—e.g. interface 5. An example of the type ofconnector that can be used and the type of dual connection that can bemade is described in U.S. Pat. No. 6,953,354. It should be noted thatfor the purposes of reading this specification, the patient interfacecan be thought of as including both the interface 5 and the conduit 3where it would be appropriate to read it in this manner.

The internal structure and components of the gases supply unit 8 willnow be described with reference to FIGS. 8, 9 and 10. The gases supplyunit 8 includes an enclosing external shell 80 which forms part of, andencloses, the gases supply unit 8. The shell 80 includes internal airpassages for ducting air passing through the gases supply unit 8, andalso internal recesses, cavities or slots into which components of thegases supply unit 8 is located in use. The shell 80 of the gases supplyunit 8 is further adapted to include an open-topped compartment 13. Inuse, humidifier chamber 9 is located within the compartment 13. Blowerunit 8 includes a heater base or heater plate, located at the bottom ofthe compartment 13. A humidifier inlet aperture 15 and humidifier outletaperture 16 are located on the wall of the compartment 13, towards thetop of the compartment 13. In the preferred embodiment, the inlet andoutlet apertures 15, 16 are aligned so as to mate with inlet and outlethumidifier ports 17, 18 located on the humidifier chamber 9, when thesystem is in use. It should be noted that other forms of humidifierinlet are possible. For example, a conduit running between the gasessupply unit 8 and e.g. the lid of the humidifier chamber 9. Also, if thehumidifier chamber is a separate item (that is, not rigidly connected tothe gases supply unit in use), the humidifier inlet aperture 15 will notbe connected directly to the humidifier chamber, but will be connectedinstead to one end of a conduit or similar leading from the humidifierinlet aperture on the gases supply unit, to the humidifier chamber.

Air from atmosphere is drawn into the shell of the gases supply unit 8through an atmospheric inlet vent 19. This vent 19 can be locatedwherever is convenient on the external surface of the shell of the gasessupply unit 8. In the preferred embodiment, as shown in FIG. 9 (viewingthe housing from underneath), the inlet vent 19 is located on the rearface of the shell of the gases supply unit 8, on the right hand side ofthe rear face (right hand side when looking forwards). In the preferredembodiment, air is drawn in through the inlet vent 19 by means of a fanunit 20 which forms part of the gases supply unit 8, and which islocated inside the enclosing external shell of the gases supply unit 8.The fan unit 20 provides a pressurised gases stream for the gases supplyunit and therefore the assisted breathing system. The fan unit 20 willbe described in more detail below. The air is drawn into the fan unit 20indirectly, via a curved inlet path 22 formed through the shell of thegases supply unit 8. Path C runs from the inlet vent 19 up over thepower supply cavity and though the venturi (shown in dotted lines) pastinto curved path 22 (including absorber foam channel and through athermistor flow sensor) to an aperture 23 formed in the gases supplyunit shell 80, the aperture 23 passing into a recess/plenum 21 which isformed in the gases supply unit shell 80, in which the fan unit 20 islocated. The air then passes into the inlet 27.

The gases stream passes through the fan unit 20 to the humidifier inletaperture 15 as follows: the shell of the gases supply unit 8 includes achamber or outlet duct 26 which forms at least part of an outlet airpath to allow gaseous communication between the fan unit 20 and thehumidifier inlet aperture 15. In the preferred embodiment, the outletduct 26 runs up between the right hand side wall of the gases supplyunit 8 (from behind looking forwards) and the front wall, up to thehumidifier inlet aperture 15. As shown in FIGS. 9 and 10, air exitingthe fan unit 20 enters the duct 26.

In use, air exits the shell of the gases supply unit or blower 8 via thehumidifier inlet aperture 15 and enters the humidifier chamber 9. In thepreferred form, the humidifier inlet aperture 15 forms an outlet at theend of the duct 26. The gases are humidified and heated in the chamber9, before passing out of the chamber 9 through the humidifier outletaperture 16, which is directly or indirectly connected to the patientoutlet 30 (it should be noted that the outlet of the humidifier chamber9 could also be completely separate from the gases supply unit 8). Theheated humidified gas is then passed to the user 1 via conduit 3. Thepatient outlet 30 is adapted to enable pneumatic attachment of thepatient conduit 3, and in the preferred embodiment, outlet 30 is alsoadapted to enable electrical connection via an electrical connector. Acombined electrical and pneumatic connection can be useful for exampleif the conduit 3 is to be heated. Electrical heating of a conduit suchas conduit 3 can prevent or minimise the occurrence of condensationwithin the conduit 3. It should also be noted that the outlet connectiondoes not have to be via the shell of the integrated unit 7. If required,the connection for the conduit 3 could be located directly on an outletfrom humidifier chamber 9.

The blower unit 8 in use is set to a user-specified pressure leveland/or the pressure level can be automatically controlled. The flow ratefor the preferred embodiment will vary during use, depending on theusers breathing. The power to fan unit 20 can be altered, to change thespeed at which the impeller 24 is rotating, and therefore the pressure.

The structure of the fan unit 20 according to one embodiment shall nowbe described, with particular reference to FIGS. 11, 12 and 13. The fanunit 20 is located in recess 21 of the shell of the gases supply unit 8in use, as described above with reference to FIGS. 9 and 10. In thepreferred form, the fan unit 20 comprises a rotating impeller locatedinside a casing having the form of a snail or scroll casing 25.

It can be seen that the fan unit 20 appears generally circular in planview, as shown in FIGS. 11 and 12. The fan casing 25 includes an inletaperture 27. In the preferred form, inlet aperture 27 is a circular holelocated in approximately the centre of the casing 25 and passing fromthe outside of the casing to the inside. Air from the inlet path 22 (seeFIG. 10) enters the fan casing 25 via the inlet aperture 27. It shouldbe noted that where it would be appropriate to include the aperture 23and at least part of the recess 21 as part of the air inlet path, thespecification should be read as including these elements. The preferredform of the casing 25 of the fan unit 20 also includes an outlet passage28.

In the preferred form, the outlet passage 28 is a short passage formedas an integral part of the casing 25 and aligned substantiallytangentially to the circumference to the remainder of the generallycircular casing 25. A fan casing outlet aperture or exit aperture 29(see e.g. FIG. 13) is located at the outer end of the passage 28. Itshould be noted that the fan casing exit aperture 29 could be locatedwherever is convenient on the passage 28 (i.e. it does not have to be atthe end of the passage, it could be through the passage wall partwayalong its length, for example). Exit aperture 29 opens into the duct 26.The outlet passage 28 forms part of the air path from the fan to thehumidifier inlet aperture 15.

The fan casing 25 encloses the fan in use, except for the inlet aperture27 and the exit aperture 29 of the passage 28. In the preferredembodiment, rotation of the fan unit 20 is driven by a motor, the fan orimpeller unit being adapted for connection to the motor. Air or gasesare drawn through inlet aperture 27 in the centre of the casing 25, intothe centre of the impeller unit 24, and are then forced outwards as agases stream through the exit aperture 29 of the outlet passage 28 bythe impeller blades 31 as the impeller unit 24 rotates.

In the preferred form, the fan outlet passage or exit passage 28 has agenerally rectangular cross-section, and the exit passage 28 is alignedsubstantially tangentially to the casing 25. However, the cross-sectionof the fan outlet passage 28 could be any suitable shape, such as oval,rectangular or circular. The fan outlet passage 28 could also bearranged at any suitable angle to the impeller unit, for example facingradially outwards, or at any suitable angle between tangential andradial. The fan outlet passage 28 causes the gases forced outwards bythe impeller unit 24 to coalesce as a fluidic gases stream, and dictatesthe direction in which the gases stream flows. The overall path oroverall direction of the gases flow will be along the passage from thefan towards the fan casing exit aperture 29.

The preferred form of the impeller is shown in FIGS. 14 and 15. Theimpeller 24 has a plurality of blades 31 extending outward from acentral hub 32. The impeller is a centrifugal impeller. The hub 32defines the axis about which the impeller rotates. Preferably the hub 32has an aperture or recess on the underside to allow engagement with amotor shaft which facilitates impeller rotation. However, otherengagement mechanisms, such as over moulding of the hub with a shaft,could be used. When the impeller is rotated, air enters the impellerblades in the region proximate the hub 32, travels radially outward andexits the blades proximate the blade tips 33. The impeller is preferablymade in one piece (“one piece construction”), as opposed to moulded inmultiple parts and joined. This is possible when there is no shroud—orat most one shroud. This reduces misalignment of components that mightlead to imbalance or other disadvantages. In the preferred embodimentthere is no shroud (in contrast with for example the shroud 152 shown inFIGS. 5 and 6.)

The blades 31 preferably provide a substantially flat surface, from thehub 32 to the blade tip, and incident the direction of rotation tothereby centrifuge gases. Preferably the tips of the impeller blade tips33 partially curve in the direction of impeller rotation (“arrow “A”).That is, the blade tips 33 are forward swept. Forward swept blade tipshelp to impart stronger rotational forces on the gases flowing throughthe impeller than straight or backswept blades. The forward swept bladetips help to produce a high pressure annulus between beyond tip of eachblade. The inner portion 31 of the impeller blade may be somewhatbackswept. A backswept blade allows for some recirculation of gases onthe blade surface itself. The backswept inner blade portion may bebeneficial to increase pressure generation and allow for stable low andreverse gases flow.

The impeller is constructed to be lightweight. Preferably, this is bymaking the impeller shroudless, or at least partially shroudless,thereby removing weight. To achieve a lightweight impeller, as shown inFIGS. 14 a and 15 a, each of the blades 31 of the preferred impeller 24are open between the blades (that is, the upper and lower “faces” or“planes” of the impeller are open to the internal surfaces of thehousing of the fan unit 20) thereby defining a shroudless centrifugalimpeller. By omitting a shroud on both the upper and/or lower faces ofthe impeller blades, the weight of the impeller 24 can be substantiallyreduced. The weight of the impeller can also be reduced in other ways,in addition to or alternatively to omitting the shroud. For example, alightweight material can be used. Also, thin blades with minimalmaterial and large gaps between blades could be implemented to reduceweight. Alternatively, a shroud 35 with some of the material removed,such as shown in FIGS. 14 b, 15 b could be used. A scalloped shaped 36shroud is provided whereby some of the material between blades 31 isremoved. Any suitable amount of material could be removed. A shroudchannels air from the impellers. Where significant material is removed,the resulting structure may in fact no longer carry out this function ofa shroud but rather just provide support for impeller blades 31. In thiscase, the impeller 24 may still be considered shroudless, despite havingsome structure between impeller blades 31. In yet a further embodimentshown in FIGS. 14 c, 15 c the structure between the impeller blades is awebbing that is disposed centrally between impellers. Such as structuredoes not function as a shroud. The reduced material structure or webbing36 can be of any shape (not just scalloped) or extent, of which FIGS. 14b, 15 b, 14 c, 15 c show two examples. A lightweight impeller 24provides benefits such as manufacturing cost, low rotational inertia andis balanced or requires little effort to rotationally balance oncemanufactured. An impeller with low rotational inertia can be quicklyaccelerated and decelerated. A lightweight, shroudless impeller istherefore suited for quickly responding to fluctuating pressurerequirements, such as the normal inhalation and exhalation cycle of apatient connected to the breathing assistance device in which theimpeller operates.

For example, a conventional shrouded impeller commonly used on abreathing assistance device, weighing approximately 17 grams and havinginertia of 6 kg·mm2, can respond to pressure fluctuations of 10 cmH2O inapproximately 2 seconds. By contrast, the preferred impeller, weighingapproximately 1.7 grams and inertia of 0.5 kg·mm2, responds pressurefluctuations of 10 cmH2O in approximately 100 ms. FIG. 29A shows a graphof pressure verses time for the earlier impeller weighing 17 grams. Theimpeller is operated to attempt to maintain a constant pressure of 4cmH2O during the normal inhalation and exhalation cycle of a patient. Incomparison, FIG. 29B shows a graph of pressure verses time for thepreferred impeller 24. It can be seen that the decrease in mass androtational inertia over the earlier impeller exhibits much less pressurefluctuation that the impeller of FIG. 29A. The reduced pressurefluctuation is less disruptive to a patient's breathing process, andtherefore advantageously increases patient comfort.

As mentioned, the lightweight can be achieved by omitting a shroud.However, it is not necessary to omit the entire shroud—rather justsufficient shroud to bring the weight of the impeller to a suitablelevel—such as shown in FIGS. 14B, 15B, 14C, 15C. Therefore, lightweightcan be achieved by having as much open space (area or volume) betweenthe blades as possible. The open space can be defined in terms of theblade volume to blade sweep volume ratio/percentage. That is, the bladessweep a volume X when rotating and the blades themselves have a combinedvolume Y (which is the volume of each blade combined). Alternatively,from a plan perspective, the open space can be defined in terms of theblade area to the blade sweep area. The ratios should be kept as low aspossible. In one embodiment, for example the swept volume of theimpeller is approximately 19,000 mm3, where the blades constitute avolume of approximately 1,200 mm3. The ratio of swept volume to bladevolume is therefore approximately 16:1, thereby defining an impellerthat is lightweight compared to the smaller, more densely designed andheavier impellers used earlier.

The lightweight impeller can have a weight for example of less than 2grams and preferably between 0.8 and 1.8 grams, or more preferably,between 1.2 and 1.7 grams, or even more preferably 1.7 grams. These arejust examples or a preferred embodiment and the impeller need not bethis weight, but some other weight that renders it lightweight.

Alternatively, a lightweight impeller can be designed to remove as muchof the shroud as necessary to bring the moment of inertia to radiusratio down to preferably less than 15 gram*mm, and more preferablybetween 8-12 gram*mm and in one possible embodiment approximately 11gram*mm. For example, in one possible embodiment, such an impeller canhave a radius of 35 mm, a circumference of 219 mm, and at 15,000 rpm amoment of inertia of 344.22, a tip speed of 54.98 m/s, a pressure of1,800 Pa and a tip speed to inertia to radius ratio of 3.5 or more andfor example 5.59. More generally, a lightweight impeller could havedimensions/parameters within the following ranges (note these ranges areindicative—not limiting): radius: 15 mm-60 mm; and/or weight: less than2 grams.

A pressure ratio to inertia to radius ratio of greater than 50:1 Pascalsper gram*mm and preferably 80:1 Pa per gram*mm or more at 1,000 Pa.

Lightweight impellers enable larger radius impellers to be used. Yetlarger radius impellers can be used than those mentioned above. Largerradius impellers provide greater tip speed and pressure. Theconstruction of the impeller allows for greater radius impellers becausethe lightweight nature of the impeller is such that even with largerimpellers, the inertia is still low enough to provide the requiredresponse and pressures.

The lightweight nature of the impeller can be achieved through removingmass through any suitable means, such as removing the shroud and/ormaterial from the impeller and/or using lighter materials. One possiblemanner in which to reduce impeller mass is to reduce the number ofblades.

The impeller generates a high pressure annulus between the tip and innerface of the housing. The backward facing impeller with a forward sweepat the tip also allows for recirculation on the blade itself, whichhelps with increased pressure generation and stable flow and reverseflows.

The fan unit 20 as shown in FIGS. 11 and 12 and described above is shownin exploded form in FIG. 16. The blower has an upper housing layer 50and a lower housing layer 51 that assemble to encapsulate a partitioninglayer 52 and the impeller 24. The blades of the impeller are open to theinternal surfaces of the upper and lower housing layers. The partitionlayer 52 and the inner surface of the upper layer 50 are profiled tosubstantially enclose the impeller blades when the layers are assembled.This forms a first interior region (“upper region”). The upper housinglayer 50 has the aperture 27 that defines the gases entry into theblower. The lower housing layer defines a volute 53 where gases arecollected before emission from the blower. Preferably the volute 53 alsohas a sealing inner wall 56. The wall 56 defines a space internal to thelower housing that may be used to house a motor. The lower housing layer51 and the partition 52 form a second interior region (“lower region”).

The outlet passage 28 of the fan unit 20 is connected to the volute 53via an aperture 54. The aperture 54 and the volute wall 53 define atongue 55 whereby gases circulating in the volute 53 are diverged intothe outlet passage 28.

The partition layer 52 is generally circular and substantially dividesthe upper housing 50 from the lower housing 51 thereby defining theupper and lower gases flow (interior) regions of the blower. To allowgases to flow from the upper region to the lower region an aperture(opening) 57 is located at, or close to the outer edge of the partition.The aperture 57 is shown more clearly in FIGS. 17 and 18. The aperture57 is most preferably an opening formed by a cut-away in the partitionlayer 52, or some other configuration/shape of the housing 51 such thatthe combination/arrangement of the partition layer 52 and the housing 51creates an aperture/opening between the two. However, the aperture 57may also comprise a flow path formed separately to the partition layer,such as a bulge or fluid channel formed in the walls of the upper 50 andlower housings 51. The cut-away could form a circumferential aperture 57between the housing 51 and partition 52, for example. Thecurvature/centre of radius of the circumferential aperture 57 ispreferable offset from the centre of radius of the partition 52 orotherwise has a curvature that differs from that of the circumference ofthe partition 52 resulting in an eccentric or otherwise offsetcircumferential aperture 57 around the circumference of the partition 52as shown in the Figures. This produces an aperture 57 with a crescent(“smile”) shaped opening that spans a leading edge 58 to a trailing edge59. However, the aperture may be of any shape with a gradual opening andclosing relative to the plane of impeller rotation. The aperture allowsfor gradual supply of pressure and flow from the high static pressuresource at the top of the blower. The angle of the aperture opening andclosing is tuned to allow for reverse flow to return through the systemin a stable fashion. It also contributes to the blade pass noisereduction by not having a sharp break in geometry. The aperture providesaddition tongues, as well as that on the outlet. The gradual opening andclosing of the aperture (“tapers”) provides tongues. The maximumvelocity at the outlet (e.g. 10 m/s) is less than that at the tapers(e.g. 60 m/s). The gradual opening and closing with blades passing atthat speed manages blade pass noise. The width and length of theaperture 57 controls the velocity in the lower (volute) section of thehousing. A wider and longer aperture increases velocity in the volute,for example.

During operation of the blower, the impeller 24 is rotated in directionA—see FIG. 17. The rotation of the impeller 24 draws gases through theinlet 27 and through the blades 31 toward the outer wall of the upperhousing layer 50. During operation, air B can also be drawn through thestator/rotor from the other side of the housing—see e.g. FIG. 13. Theair B drawn through can cool the motor. The shroudless impeller 24enables air to be drawn through the motor in this manner thus providingcooling. The forward swept blade tips 31 impart strong rotational forcesto the gases circulating in the upper region of the blower housing tothereby create high circulating gas speeds. Gases in the upper regionwill naturally flow through the aperture 57 to the lower region due topressure differential between regions. When the gases in the upperregion, having a high velocity and low pressure, enter the lower region,specifically the volute 53, the gas velocity drops and the pressureincreases. Typically the volute 53 has a greater volume than the upperregion to help facilitate a gases pressure increase.

By dividing the blower internal space into two separate regions a numberof advantages can be realised. In a conventional blower, high velocitygases leaving the impeller are incident to the edge, or tongue, thatdefines a physical boundary where gases are split from the volute toenter the outlet passage. High velocity gas flow at incident the tongueis turbulent and inefficient to blower performance. The turbulencecaused by the tongue reduces also introduces a source of noise. Incontrast, dividing the housing of the preferred blower into the upperand lower regions reduces the impact caused by the tongue. The upperregion allows the gases to circulate at a high speed. The gradual radialopening and closing of the preferred partition 57 provides a fluid pathto the lower region that is free from (or has reduced) aerodynamicallyturbulent edges. When circulating gases have entered the lower region,the enlarged volume of the volute encourages the gases to slow andincrease pressure. The reduced gases velocity reduces the impact ofturbulence normally caused by the tongue 55 to a low or negligiblelevel. The blower unit is therefore able to operate across a widepressure and flow range with substantially reduced noise output whencompared to other blowers. A wider and longer aperture 57 increases theflow rate of the lower region relative to the upper region. Therefore,the size of the aperture is selected according to the desired flow rateand pressure range of the blower unit.

The motor used to drive the impeller 24 is shown in cross section inFIG. 19. Preferably the motor is a brushless DC motor operated usingsensorless vector control (also termed “field oriented control”)controlled by a microcontroller, microprocessor or similar controller 14(such as shown in FIG. 7), for example, via the connector 131 mounted toa PCB 130. The control can be tuned to suit a low inertia impeller. Thecentral hub 32 of the impeller 31 is engaged with a shaft 60 thatextends from the motor 61. Mounted to the shaft is a plurality of,preferably small, magnetic segments to form a rotor 62. In oneembodiment the magnet is 20 mm in diameter, but more generally thediameter could be less than 20 mm and preferably between 10 mm to 15 mm.The magnet volume is less than 1600 mm3 and can be between 500 mm3 and1600 mm3. Surrounding the rotor 62 is a laminated stator having aplurality of poles 63 and windings 68. The stator is mounted to the PCBor other substrate 130 and the windings coupled to the connector 131.The windings are selectively energised by the microcontroller 14 via theconnector 131 to facilitate rotation of the rotor, and therefore theshaft 60 and impeller 31, about the central axis defined by thecentreline of the shaft 60.

The shaft 60 is held within the motor by a bearing structure. Preferablythe bearing structure has one or more bearings 64 and one or morebearing mounts 65. The bearing mounts 65 as shown engage with thebearings on an inner surface and with the stator on an outer surface.The preferred engagement of the mount to the bearings and the stator isfrictional. To promote a frictional engagement, the bearing mounts 65are made of a soft, yet resilient and/or flexible material such assilicone rubber or other elastomeric material. The material can be lowcreep, temperature stable, low compression set with a high tan delta(highly viscous), highly damped. Examples comprise: Dough MouldingRubbers like—NBR, Nitrile and Flouro silicone; Thermo Plastic Elastomers(TPE's) like Santoprene by Exxon; Thermo Plastic Urethanes likeDynaplast by GLS Corporation; Heat Cured Casting Urethanes like 10T90 byNational Urethanes; and multiple other cold cast rubbery compounds likeRTV (Room Temperature curing Vulcanites) by Dow Corning, Whacker andothers. In another embodiment, bushings (rubber or otherwise) could beused instead of bearings.

Such materials allow the mounts 65 to compress when installed, thenexpand into their chosen location to be held in place by engagementexpanded dimension with a restriction. The mounts 65 are optionallyrestrained by an overhang 66 formed as part of an electricalinsulator/isolator or other frame structure (“stator frame”) on thestator. Similarly, the bearings may be restrained by an overhang 67formed as part of the bearing mount. Either or both of the overhangs maybe discretely positioned about the inner and outer annulus of thebearing mounts, or alternatively, extends around the circumference ofthe mount to define a recess in which the mount is located.

The bearing mounts provide compliance to the rotatable shaft 60. Asrotatable objects, such as the rotor 62, shaft 60 and impeller 31usually suffer from some degree of rotational imbalance, the bearingmounts are able to isolate inherent rotation induced vibration from themotor rotor. It has been found that combination of the lightweight,shroudless impeller having a low rotational inertia, as described above,together with the given compliance of the bearing mounts enables therotor 62, shaft 60 and impeller 31 to be manufactured and any postmanufacture balancing process for the rotating components entirelyomitted. These advantages benefit manufacturing costs and time. Thelightweight nature of the impeller allows any imbalances to becompensated by the bearing mounts. A lightweight impeller also allowsfaster speed response of the impeller to changing conditions. Anyunwanted fluctuations in pressure due the lack of shroud can becompensated for by quickly changing the impeller speed to returnpressure to the desired level.

It should be noted that while FIG. 19 shows the bearing mounts 65mounted within the motor stator, they may equally be housed externallyto the motor. For example, the mounts 65 may instead be mounted withinjournals formed within the blower housings, or the gases supply unit 7.In such circumstances where the bearing mounts are located within thegases supply unit 7, it may also be advantageous to omit discretestructures for the blower housing 50, 51, instead mounding the innersurfaces of the housings directly to the internal structure of the gasessupply unit 7.

To provide further vibration damping of the rotational components of theblower, the motor and impeller, can optionally be mounted on a compliantmounting device. FIG. 20 shows one embodiment of such a mounting device70. In accordance with the preferred embodiment of the invention themount is most preferably made from a soft, flexible yet resilientmaterial such as silicone rubber. The mounting device 70 has an internalrecess 71 in which the stator is relieved. Preferably the internalrecess is smaller than the outer surface of the motor to encourage aninterference fit between these components. FIG. 21 shows the motor 61positioned within the mounting recess 71.

A plurality of projections 72 encircles the upper and lower surfaces ofthe mount 70. Each projection 72 preferably has a base recessed into thebody of the mount to effectively increase the length whereby theprojections are free to bend. The end of projection extends past theupper and lower surfaces of the mount to provide supporting leverage tothe mount and motor assembly. During operation of the motor, vibrationcaused by any imbalance of the rotational components is absorbed by eachof the projections by allowing the body of the mount 70 to move relativeto the surface on which the projections 72 are supported.

FIG. 22A is a graph of the sound pressure level of a conventional fanunit tested in an anechoic chamber. FIG. 22B is a graph of the soundpressure lever of a fan unit according to the present invention. It canbe seen that the lightweight and shroudless impeller 24, the flexiblebearing mounts 65 and flexible motor mount 70 contribute to asignificantly reduced noise output across the tested spectral range of50 Hz to 10 kHz.

A further embodiment of the motor and impeller assembly is shown inFIGS. 23 to 28. Many aspects of this embodiment are the same as those inthe previous embodiment. Features described in relation to the previousembodiment not described in this embodiment can be assumed to exist inthis embodiment where appropriate. Like features will use the samereference numerals as the previous embodiment. The motor used to drivethe impeller 24 is shown in cross-section in FIG. 27. Preferably themotor is a brushless DC motor operated using sensorless vector control(“field oriented control”) controlled by a microcontroller,microprocessor or similar controller 14 (such as shown in FIG. 7), forexample, via a connector 231 mounted to a PCB/substrate 230 (such asshown in FIG. 23). The control can be tuned to suit a low inertiaimpeller. Referring to FIGS. 23, 24 and 27, the central hub 32 of theimpeller 24 is engaged with a shaft 60 that extends from the motor 61.Mounted to the shaft is a plurality of, preferably small, magneticsegments to form a rotor 62. Surrounding the rotor 62 is a laminatedstator 241 having an annular outer portion 242 and a plurality of poles243 and windings 68. The stator is mounted to the PCB or other substrate230 and the windings 68 coupled to the connector 231. The stator 241 hasan electrical insulator/isolator (forming a stator frame) 270 a, 270 bcovering the top and bottom of the annular portion 242 and the poles243. Each winding 68 is preferably assembled on the insulator 270 a, 270b over each pole 243. Protrusions for engagement and retainment areprovided around the circumference 271 extending upwards and at the endof the poles extending upwards 272 a and downwards 272 b.

Referring to the plan view of one of the laminations 240 in FIG. 24,each lamination comprises an annular outer portion 242 and a poleportion 243 extending radially inwards. The edge 244 of each poleportion 243 includes a wave shape. The wave shape comprises two concaveportions 244 a, 244 b meeting at a central apex 244 c. Referring to FIG.25, when a plurality of the laminations 240 are stacked to create thestator 241, each pole 243 has an inner radial face 250 with a wave shapeas shown in FIG. 25. The face 250 comprises two concave portions 250 a,250 b meeting at a central apex 250 c. This arrangement reduces cogging.The stator and/or rotor can have a skewed magentisation. The windingsare selectively energised using the controller 14 via the connector 231to facilitate rotation of the rotor, and therefore the shaft 60 andimpeller 31, about the central axis defined by the centreline of theshaft 60.

The shaft 60 is held within the motor by a bearing structure. Preferablythe bearing structure has one or more bearings 64 and one or morebearing mounts 260 (see FIG. 26). The bearing mounts 260 as shown engagewith the bearings 64 on an inner surface 261 and with the stator241/insulator 270 a/270 b on an outer surface as shown in FIG. 27. Thebearing mount 260 comprises a main annular body 265 that curves from alow point at a central aperture 263 to a higher point at the outercircumference 262. The outer circumference comprises an engaging lip264, preferably with a chamfer 264 a on the intersection of the outercircumference 262 with the main annular body 265. The intersection ofthe inner aperture 263 with the inner circumference 261 of the main body265 also preferably has a chamfer 261 a. An annular wall/boss 266extends upwardly from the main annular body 265 at the inner aperture263. The top portion 267 of the annular wall 266 has an overhangingengagement lip 268. The intersection of the lip 268 with the annularwall 266 and with the overhanging lip side wall 268 a are preferablychamfered 268 b, 268 c. The preferred engagement of the bearing mount260 to the bearings 64 and the stator 241 is frictional. To promote africtional engagement, the bearing mounts 260 are made of a soft, yetresilient and/or flexible material such as silicone rubber or otherelastomeric material. The material can be low creep, temperature stable,low compression set with a high tan delta (highly viscous), highlydamped. Possible materials were described in relation to the previousembodiment. Such materials allow the mounts 260 to compress wheninstalled, then expand into their chosen location to be held in place byengagement expanded dimension with a restriction. They also providecompliance.

FIG. 27 shows the bearing mounts in solid lines in theuninstalled/unassembled state, with an upward curvature. The dottedlines show the bearing mounts 260 in the installed/assembled state,clipped in to the stator/insulator 279 a, 270 b. In the installed state(also called engaged state or configuration) the annular body is engagedwith the stator 241 and/or stator frame 270 a, 270 b and the annularbody 265 is coerced from the curved state (shown in solid lines) into anengaged (flat) configuration (shown in dotted lines) that providespreload to the one or more bearings by action of the bearing mountproviding bias provided by the resilient/flexible body acting on thestator and/or stator frame and the bearings. The mounts 260 areoptionally restrained by an overhang 272 c, 272 d formed on theinsulator 270 a, 270 b. Similarly, the bearings 64 may be restrained byan overhang 268 formed as part of the boss 266 on the bearing mount 260.Either or both of the overhangs may be discretely positioned about theinner and outer annulus of the bearing mounts, or alternatively, extendsaround the circumference of the mount to define a recess in which themount is located. The impeller/shaft/rotor is assembled into the stator241 by assembling the bearings 64 on the shaft 60, assembling thebearing mounts 260 on the bearings 64 and manipulating the bearingmounts 260 (by hand, jig or other means) so they engage with the statorinsulator 270 a, 270 b at each pole 243. In an alternative embodiment,the bearing mounts 260 are not coupled directly to the stator orinsulator 270 a/241 but rather are coupled to another structure such asa housing. Any coupling arrangement with any suitable structure can beprovided which provides the required functions as set out below.

The bearing mounts 260 provide compliance to the rotatable shaft 60. Asrotatable objects, such as the rotor 62, shaft 60 and impeller 24usually suffer from some degree of rotational imbalance, the bearingmounts are able to isolate inherent rotation induced vibration from themotor rotor. It has been found that combination of the lightweight,shroudless impeller having a low rotational inertia, as described above,together with the given compliance of the bearing mounts enables therotor 62, shaft 60 and impeller 24 to be manufactured and any postmanufacture balancing process for the rotating components entirelyomitted. These advantages benefit manufacturing costs and time. Thelightweight nature of the impeller 24 allows any imbalances/misalignmentto be compensated by the bearing mounts 260—the arrangement is selfaligning due to the bearing mount compliance (due to resilience and/orflexibility, for example). The bearing mount construction, including thegeometry and material, also provides axial preload on the bearings, e.g.of up to 7 Newtons. The annular nature of the bearing providesconsistent/even preload around the bearing 64. The resilient/flexiblecurved annular body allows the bearing to be installed in place andprovide the preload. The annular nature of the bearing mount 260provides for even preload around the bearing, while the low creepconstruction material maintains preload. The material of the bearingmounts 260 is also preferably a viscoelastic damping material thatprovides damping, which reduces the likelihood of resonance duringoperation of the motor. Such a viscoelastic material can also providethe required resilience/flexibility to provide the preload. An exampleof such a material is a Thermo Plastic Urethane like Dynaplast by GLSCorporation. Other materials resilient and/or flexible materialsmentioned above for the bearing mount 260 could be adapted to providethe required damping by adding mica. A lightweight impeller also allowsfaster speed response of the impeller to changing conditions. Anyunwanted fluctuations in pressure due the lack of shroud can becompensated for by quickly changing the impeller speed to returnpressure to the desired level. The bearing mounts also provide vibrationisolation.

To provide further vibration damping of the rotational components of theblower, the motor and impeller, can optionally be mounted on a compliantmounting device (motor mount) 280. FIGS. 23, 27 and 28 shows oneembodiment of such a mounting device 280. In accordance with thepreferred embodiment of the invention the mount is most preferably madefrom a soft, flexible yet resilient material such as silicone rubber.The mounting device 280 has an annular body 282 with upper and lowerengaging lips 282 a, 282 b that define an internal recess 281 in whichthe stator 241 is disposed. Preferably the internal recess 281 issmaller than the outer surface of the stator to encourage aninterference fit between these components. FIG. 27 shows the motorpositioned within the mounting recess 281.

A plurality of projections 283 encircles the upper and lower surfaces ofthe mount 280. The end of projection extends past the upper and lowersurfaces of the mount to provide supporting leverage to the mount andmotor assembly. During operation of the motor, vibration caused by anyimbalance of the rotational components is absorbed by each of theprojections by allowing the body of the mount 280 to move relative tothe surface on which the projections 283 are supported.

The description above describes embodiments of a blower comprising alightweight impeller assembly. FIGS. 19 and 27 show embodiments with ametal (e.g. steel) shaft 60 assembled on a magnet rotor 62. The metalshaft is press fit into an aperture in the magnet rotor. This requiresfine tolerance control to ensure a good tight fit to reduce slipping.However, the fit should not be so tight as to risk cracking the magnetrotor.

Alternative shaft and magnet rotor assemblies are shown in FIGS. 30 to33B, which can be used in the stator in place of the assembly shown inFIG. 19 or 27.

FIGS. 30A, 30B and 31 show a possible alternative rotor assembly of theembodiments described above. The assembly comprises a metal shaft 300(see FIG. 31) and a magnet rotor 301. The magnet rotor 301 has a centralopening 302. The central opening 302 comprises a central portion withindents 303 a to 303 d. The central opening also comprises a profilededge through a central cross-section providing a stepped ledge 308 (seeFIG. 30B). The metal shaft 300 has a knurled section 309 b in itsexterior and extends through the central opening 302. A plastic insert303 is injection moulded between the shaft 300 and the magnet rotor 301in the central opening 302. The plastic insert 303 is overmoulded ontothe stepped ledge 308 of the magnet rotor. This provides an insert 303with a similar exterior shape to the central opening 302. Aninterlocking (cog dog) is formed between the shaft 300 and overmoulded(insert) material 303, so that the metal shaft knurled section 309 bengages with the overmoulded insert 303 to couple the shaft 300 to themagnet rotor 301. The assembly 304 can be used in the embodimentsdescribed above such as an FIGS. 19 and 27, wherein the shaft 60 andmagnet rotor 62 of those embodiments are replaced with the metal shaft300/plastic insert 303/magnet rotor 301 assembly 304 as described inFIGS. 30A, 30B and 31. The assembly can be created as shown in FIG. 34.The rotor is placed in a mould, step 340, the shaft is introduced, step341, the other mould half is introduced, step 342, the insert isinjection moulded between the shaft/rotor, step 343, and then the mouldremoved, step 344.

FIG. 32 shows plan, elevation and isometric views of a magnet rotor andshaft assembly 320 according to another alternative embodiment. Theassembly 320 comprises a rotor 301 formed from a magnet material. Themagnet rotor 301 has a central opening 302. The central opening 302comprises a central portion with indents 303 a to 303 d. The centralopening also comprises a profiled edge through a central cross-sectionproviding a stepped ledge 308.

The assembly 320 also comprises a plastic shaft 321 that extends throughthe centre of the insert opening 310 and is overmoulded onto the magnetrotor 301 as will described below. When overmoulded, the shaft comprisesan integral overmould magnet insert portion 323. The shaft 321 can beformed to comprise a hex 322 or other location profile for press fitcoupling with the impeller 24. The plastic shaft 321 comprises anysuitable plastic or combination thereof, such as acety or polypropylene,although any suitable injection moulding or other plastic could be used.

The assembly 320 can be used in the embodiments described above such asan FIGS. 19 and 27, wherein the shaft 60 and magnet rotor 62 of thoseembodiments are replaced with the plastic shaft 321/magnet rotor 301assembly 320 as described in FIG. 32.

FIGS. 33A and 33B show an injection moulding tool that can be used tomanufacture the shaft/rotor assembly 320, and FIG. 35 is a flow diagramof a method of manufacture. The tool 320 is an open and close two-partmould tool comprising a first mould part/portion 331 a and a secondmould part/portion 331 b that come together to form a mould/cavity 332comprising a magnet jig 333. The mould comprises a cavity to form theshaft 321, hex fit shape 322 and overmould portion 323. Duringmanufacture of the assembly 320, a magnet rotor 301 with an opening 302as described above is introduced into the mould and placed in positionin one half of the mould forming the jig 333, step 350. The top portion321 a of the mould is placed in position to create the mould cavity 332with the bottom portion 321 b, step 351. An injection moulding processstarts, step 352, to injection mould plastic to create the shaft 321overmoulded onto the magnet rotor 301. The injection moulding processovermoulds plastic over the stepped ledge 308 portion of the rotormagnet 301 to create the insert portion 323. Once the injection mouldingprocess is complete, the mould portions 321 a, 321 b are removed leavingthe assembly 320, step 353. The assembly 320 can then be used in themotor of FIG. 19 or FIG. 27, for example.

Previously, it has not been possible to use a plastic shaft/rotorassembly in the motor of a blower of a CPAP machine or similar. Aplastic shaft is not sufficiently strong to withstand the forcesinvolved in such motors. However, in the lightweight impellerembodiments described above, the forces are such that a plastic shaftrotor becomes a possibility. The lightweight and low inertia nature ofthe rotor along with the compliant bearing mount and other features thatreduce unbalancing forces and other forces enable the use of a plasticshaft. Both the plastic rotor assembly and the method of manufactureprovide advantages over existing metal shaft rotors.

The combination of various features of the present invention provideadvantages, which can be achieved using a single impeller. Using alightweight/low inertia impeller (e.g. by removing some or all of theshroud and/or reducing blade material) reduces imbalance of the impellerdue to manufacturing tolerances. Previously, after manufacture andduring assembly of a blower, it has been necessary to remove/addmaterial to the impeller to improve balancing. The lightweight nature ofthe impeller means that any small imbalance can be tolerated withoutrequiring rectification. Coupled to this, where the imbalance is notsmall enough, the resilient/flexible bearing structure mounts 65 and/orstator mount can compensate for any imbalance in the impeller. As theimpeller is lightweight enough, any imbalance is of a small enoughmagnitude to be compensated for by the bearing structure mounts 65,without the need for altering the weight of the impeller duringassembly.

The lightweight construction also allows for a larger diameter impeller,which in turn provides higher tip speed for a particular RPM. Thisallows for lower RPM operation of the blower while still achieving therequired pressure (which is dependent on tip speed). Having a lower RPMreduces vibration to an acceptable level, or to a level that can becompensated for by the bearing structure and/or stator mount. Thelightweight construction of the impeller as mentioned previously enablesthe larger impeller as it provides lower inertia that achieves therequired pressures/response. That is, lower torque is required to speedup and slow down the impeller to reach the required tipspeeds/pressures. This improves dynamic performance (response). Inaddition to this, small magnets in the motor (combined with the bearingstructure) remove the need for balancing during assembly, improvedynamic performance.

The resilient/flexible bearing structure allows for self-alignment,compliance, damping and preload of the impeller and shaft assembly. Thismakes assembly easier, and in combination with the lightweight/lowinertia impeller reduce or negates the need for balancing modificationsduring assembly, as mentioned previously. The bearing structure providesfor relaxed tolerances during manufacture as it compensates for largertolerances. The bearing structure also isolates and/or damps vibrations,also allowing high RPM speeds of the impeller where necessary. Thestator frame/motor mount also provides vibration isolation.

The partition that separates the blower into first and second regionsseparates out the high velocity region to reduce noise. This allows forand maintains a constant high velocity of flow while diffusing thevelocity to pressure.

The use of a plastic shaft also provides a number of benefits over ametal (e.g. steel) shaft, including (but not limited to) the following

The reliability risks associated with dissimilar materials are reduced.

The knurled interface between the cog/dog insert and the shaft does nothave to be monitored for cracking, slipping, run out, shrinkage, fluidingress/corrosion.

The impeller to shaft interface is improved and carries similar reducedreliability risks. It is less prone to cracking because of similarthermal expansion (due to plastic on plastic press fitting). There isreduced chance of slipping because of the opportunity to add some keyingfeature like a hex or grooves.

The plastic shaft assembly is a press fit rather than a sliding fit sois more stable with less chance of rattles.

The cost relative to a metal shaft is reduced. This is because of thefollowing.

Manufacturing the shaft to the tolerance for a sliding fit is notrequired because the plasticity of the plastic shaft allows for muchwider tolerance or inaccuracy to press fit the bearings.

The need for grinding of the shaft after knurling to re-establishstraightness is not required.

The handling and inserting the shaft into the mould is not required.

It is possible to use materials with better vibration absorptionproperties than steel.

Ease of assembly can be improved by reducing the length of the bearingpress fit engagement by reducing shaft diameter with a hex, undercuttingthe impeller side of the shaft.

In general, the following advantages are provided for by the combinationof one or more features as follows:

Advantage Features providing advantage Low noise impeller Low RPM (dueto large diameter impeller) Partition to provide two regions, onecontaining the impeller Low cogging torque Sensorless vector drive/fieldoriented control Fast responding blower Low inertia impeller (achievedthrough shroudless/lightweight construction) Small magnet with diameterless than 20 mm Sensorless vector drive Lower cost No balancing requiredduring assembly Small volume magnet Simple bearing mount One pieceimpeller Assembly without balancing Low inertia impeller/lightweightFlexible/resilient bearing structure Motor mount/stator frame isolatorLow RPM impeller Small magnet with diameter less than 20 mm One pieceimpeller Large diameter impeller/ Low inertia impeller Low RPMSimplified manufacture, lower Use of plastic shaft which becomes costs,better reliability possible due to lightweight impeller, balancingadvantages and other features

Although the present invention has been described in terms of a certainembodiment, other embodiments apparent to those of ordinary skill in theart also are within the scope of this invention. Thus, various changesand modifications may be made without departing from the spirit andscope of the invention. For instance, various components may berepositioned as desired. Moreover, not all of the features, aspects andadvantages are necessarily required to practice the present invention.Accordingly, the scope of the present invention is intended to bedefined only by the claims that follow.

1. A breathing assistance apparatus comprising: a pressurised gasessource comprising: a gases inlet, a gases outlet adapted to emitpressurised gases to an outlet of the breathing assistance apparatus,and a lightweight impeller on a rotatable plastic shaft.
 2. A breathingassistance apparatus according to claim 1 wherein the lightweightimpeller is shroudless or otherwise has reduced material.
 3. A breathingassistance apparatus according to claim 1 wherein the breathingassistance apparatus further comprises a motor with a stator, whereinthe rotatable plastic shaft is located within the stator, and the motorfurther comprises at least one bearing structure to support therotatable plastic shaft within the stator, the bearing structure havingone or more bearing mounts.
 4. A breathing assistance apparatusaccording to claim 3 wherein the bearing mounts provide compliantsupport to the rotatable shaft.
 5. A breathing assistance apparatusaccording to claim 3 wherein the motor further comprises a rotor withinthe stator, the plastic shaft being formed and coupled to the rotor byinjection moulding.
 6. A breathing assistance apparatus comprising: amotor comprising a rotatable plastic shaft located within a stator, abearing structure to support the rotatable shaft in the stator, thebearing structure having one or more bearing mounts.
 7. A breathingassistance apparatus according to claim 6 wherein the bearing mountsprovide compliant support to the rotatable shaft.
 8. A breathingassistance apparatus according to claim 6 wherein the motor furthercomprises a rotor within the stator, the plastic shaft being formed andcoupled to the rotor by injection moulding.
 9. A breathing assistanceapparatus comprising: a pressurised gases source comprising: a housing agases inlet, a gases outlet adapted to emit pressurised gases to anoutlet of the breathing assistance apparatus, a motor with a rotatableplastic shaft and at least one bearing structure to support therotatable shaft within a stator, the bearing structure having one ormore flexible and/or resilient bearing mounts to provide complianceand/or preload and/or damping for the rotatable shaft, a lightweightimpeller coupled to the rotatable plastic shaft, a flexible and/orresilient motor mount that couples the stator and the housing to providecompliance and/or damping for the motor, a partition to define first andsecond interior regions within the housing, wherein the first and secondregions are fluidly connected by a crescent shaped opening formed in orby the partition.
 10. A breathing assistance apparatus according toclaim 9 wherein the lightweight impeller is shroudless or otherwise hasreduced material.
 11. A breathing assistance apparatus according toclaim 9 wherein the motor further comprises a rotor within the stator,the plastic shaft being formed and coupled to the rotor by injectionmoulding.
 12. (canceled)
 13. (canceled)
 14. An assembly for a motorcomprising a plastic rotatable shaft extending through an opening in amagnet rotor and being coupled thereto.